Semiconductor device and fabrication method

ABSTRACT

A semiconductor device in one embodiment has a first connection region, a second connection region and a semiconductor volume arranged between the first and second connection regions. Provision is made, within the semiconductor volume, in the vicinity of the second connection region, of a field stop zone for spatially delimiting a space charge zone that can be formed in the semiconductor volume, and of an anode region adjoining the first connection region. The dopant concentration profile within the semiconductor volume is configured such that the integral of the ionized dopant charge over the semiconductor volume, proceeding from an interface of the anode region which faces the second connection region, in the direction of the second connection region, reaches a quantity of charge corresponding to the breakdown charge of the semiconductor device only near the interface of the field stop zone which faces the second connection region.

RELATED APPLICATIONS

This Application is a Continuation Application of application Ser. No.12/416,935, which was filed on Apr. 2, 2009 now U.S. Pat. No. 8,003,502.Application Ser. No. 12/416,935 is a Continuation Application of11/241,866, which was filed on Sep. 30, 2005 now U.S. Pat. No. 7,514,750and which claimed benefit of German Patent Application No. 10 2004 047749.3, which was filed on Sep. 30, 2004. The priority and entirecontents of application Ser. Nos. 12/416,935 and 11/241,866 and GermanPatent Application No. 10 2004 047 749.3 are hereby claimed andincorporated herein by reference.

BACKGROUND

The invention relates to a semiconductor device and to a fabricationmethod suitable therefore.

If semiconductor devices are intended to have a soft switchingbehaviour, they must be designed in such a way as to avoid currentchopping during switching. Current chopping occurs for example duringhard commutation of diodes. The consequence of such current chopping isthat severe voltage or current oscillations occur. If such oscillationsexceed maximum values permissible for the diode, then destruction of thediode may occur. Destruction of the diode may also be caused byexcessive interference effects on driving processes which are broughtabout by the current or voltage fluctuations, and resultant incorrectbehaviour of the driving processes. The problem area described aboveoccurs particularly in the case of circuits having high leakageinductance, high currents (for example in the case of powersemiconductors being connected in parallel to a great extent) and athigh voltages with respect to which the diode is commutated.

In order to realize diodes having a soft switching behaviour, thethickness of the diodes has been designed such that at maximum voltagethe space charge zone that forms, proceeding from the pn junction formedby the p-doped anode region and the adjoining lightly n-doped baseregion in the semiconductor volume, does not reach the highly n-dopedrear-side emitter. However, this entails high on-state losses andswitching losses, since the overall losses of semiconductor devices, inparticular bipolar semiconductor devices, increase approximatelyquadratically with the thickness of the lightly doped base region (chipthickness). A soft switching behaviour is difficult to realizeparticularly for high-voltage devices (having a rated voltage of morethan 150 V, in particular starting from a rated voltage of approximately500 V), since a basic material with a doping concentration that issignificantly lower than would be necessary for achieving the requiredreverse voltage is usually used for fabricating such components. The lowdoping concentration of the basic material serves for realizing the DCvoltage blocking stability of the semiconductor device, which in turnnecessitates sufficiently low field strengths at the anode and in theregion of the edge termination of the semiconductor device. The lowbasic doping has the effect that the space charge zone propagates veryfar, which has to be compensated for by means of a large chip thicknessof the semiconductor device if the intention is to ensure that the spacecharge zone does not reach the rear-side emitter.

In order to keep down the chip thicknesses, it has been proposed tointroduce a field stop zone, that is to say a zone of increased doping,in the semiconductor volume of the semiconductor device, which zone maybe configured in stepped fashion, for example. FIG. 1 shows acorresponding doping profile 1 with a stepped field stop zone using theexample of a diode. What is disadvantageous in this case is thatdifficult and expensive processes are required for producing thestepped, inhomogeneous doping profile 1: thus, an epitaxial method isrequired for example for fabricating the doping profile (the high dopingof the carrier substrate on which the epitaxial layer is deposited isnot illustrated in FIG. 1). As an alternative, it is possible to use adiffusion process, but this would take up about 100 hours at a processtemperature of 1200° C. and so is not very suitable in practice. Adoping profile 2 that can be produced by means of such a diffusionprocess is likewise indicated in FIG. 1.

SUMMARY

The semiconductor device has a first connection region, a secondconnection region, and a semiconductor volume arranged between the firstand second connection regions, there being provided within thesemiconductor volume, in the vicinity of the second connection region, afield stop zone for spatially delimiting a space charge zone that can beformed in the semiconductor volume. The dopant concentration profilewithin the semiconductor volume is configured such that the integral ofthe ionized dopant charge over the semiconductor volume, proceeding froma pn junction provided between the first connection region and the fieldstop zone, in the direction of the second connection region, reaches aquantity of charge corresponding to the breakdown charge of thesemiconductor device only near the interface of the field stop zonewhich faces the second connection region, the pn junction being the lastpn junction before the field stop zone, relative to a direction pointingfrom the first connection region to the second connection region.

The semiconductor device according to the invention can be embodied inparticular as a diode or as an IGBT (insulated gate bipolar transistor).A diode according to the invention has a first connection region, asecond connection region, and a semiconductor volume arranged betweenthe first and second connection regions, there being provided within thesemiconductor volume, in the vicinity of the second connection region, afield stop zone for spatially delimiting a space charge zone that can beformed in the semiconductor volume, and an anode region adjoining thefirst connection region. The dopant concentration profile within thesemiconductor volume is configured such that the integral of the ionizeddopant charge over the semiconductor volume, proceeding from aninterface of the anode region which faces the second connection region,in the direction of the second connection region, reaches a quantity ofcharge corresponding to the breakdown charge of the semiconductor deviceonly near the interface of the field stop zone which faces the secondconnection region.

The IGBT according to the invention has a first connection region, asecond connection region, and a semiconductor volume arranged betweenthe first and second connection regions, there being provided within thesemiconductor volume, in the vicinity of the second connection region, afield stop zone for spatially delimiting a space charge zone that can beformed in the semiconductor volume, and a body region adjoining thefirst connection region. The dopant concentration profile within thesemiconductor volume is selected such that the integral of the ionizeddopant charge over the semiconductor volume, proceeding from aninterface of the body region which faces the second connection region,in the direction of the second connection region, reaches a quantity ofcharge corresponding to the breakdown charge of the semiconductor deviceonly near the interface of the field stop zone which faces the secondconnection region.

If this condition is met, then the space charge zone reaches far intothe semiconductor volume when a reverse voltage is present, but isincreasingly curbed as the reverse voltage rises. The spatialutilization of the semiconductor volume by the space charge zone is thusoptimized. Furthermore, by meeting the conditions mentioned above it isguaranteed that during the switching operation, the increase in thereverse voltage is always associated with the depletion of a chargepacket of flooding charge present. This prevents an abrupt rise in thevoltage during the switching of the semiconductor device and thusguarantees a soft switching behavior.

The thickness of the field stop zone, which is generally configured inlayered fashion, should be more than 5%, preferably between 20% and 40%,of the thickness of the semiconductor volume, that is to say that theprofile of the field stop zone should be configured in a manner leadingout deeply (reach deep into the semiconductor volume). In a preferredembodiment, the dopant concentration profile is designed as a curvedprofile with a plurality of maxima (peaks), in which case the height ofthe peaks should increase, or at least not decrease significantly in thedirection toward the second connection region.

The field stop layer may directly adjoin the second connection region,or else be spaced apart from the latter.

Preferably, the thickness of the field stop zone is a maximum of onethird of the base width of the semiconductor volume, the base widthbeing defined as the distance between the last pn junction before thefield stop zone and the interface of the field stop zone which faces thesecond connection region.

If the semiconductor device is configured as a diode, then a cathoderegion adjoining the second connection region is formed within thesemiconductor body. If the semiconductor device is designed as a diode,the doping concentration within the field stop zone is preferably 10 to30 times the basic doping of the semiconductor volume. Furthermore, thebreakdown charge for typical basic dopings is approximately 1.8*10¹²doping atoms/cm².

If the semiconductor device according to the invention is configured asan IGBT, then a rear-side emitter adjoining the second connection regionis formed within the semiconductor device. The field stop layer maydirectly adjoin the rear-side emitter, or else be spaced apart from thelatter.

The invention can be applied, in principle, to all semiconductor deviceshaving a field stop zone, e.g. bipolar transistors, GTOs (gateturn-off), MOS transistors, etc.

The invention furthermore provides a method for fabricating a field stopzone within a semiconductor device according to the invention. In thismethod, the semiconductor volume is exposed to a plurality of protonirradiations and at least one heat treatment step, the accelerationenergies and proton doses of the respective proton irradiations and alsothe temperature of the heat treatment step or of the heat treatmentsteps being chosen so as to produce the required dopant concentrationprofile.

Preferably, radiation is effected through the second connection region(rear-side), that is to say—in the case of a semiconductor device with avertical construction—through the rear-side of the semiconductor device.In principle, it is also possible to radiate through the top side of thesemiconductor device, that is to say through the first connectionregion. However, higher irradiation energies would be necessary in thiscase.

If the semiconductor device is designed as an IGBT device, in apreferred embodiment the highest energy of the protons used during theimplantation is at least 1 MeV, and the lowest implantation energy usedis a maximum of 500 keV. It is thus possible, for example, to performthree proton irradiations of the semiconductor volume which have thefollowing implantation energies: 300 keV, 500 keV and 1 MeV. As analternative four proton irradiations of the semiconductor volume may beperformed, the corresponding energy doses being 300 keV, 500 keV, 1 MeVand 1.25 MeV.

Heat treatment processes that are effected at a temperature of 350 to420° C. are carried out between the proton irradiations or after protonirradiations. As an alternative, heat treatment processes attemperatures of 420 to 550° C. may be effected between or after theproton irradiations.

Preferably, an irradiation dose of approximately 1*10¹³ protons/cm² ischosen for the purpose of producing doping regions situated deeper inthe semiconductor volume (large distance from the second connectionregion), while an irradiation dose of approximately 5*10¹³ protons/cm²is chosen for the purpose of producing doping regions situated nearer tothe surface of the semiconductor volume (small distance with respect tothe second connection region). In this case, the sum of all theirradiation doses is intended to be 5*10¹³ protons/cm² to 50*10¹³protons/cm².

If the semiconductor device is intended to be designed as a diode, thenin a preferred embodiment the irradiation doses of the individual protonirradiations are 0.5*10¹³ to 20*10¹³ protons/cm². The sum of all theirradiation doses of the individual proton irradiations should be 5*10¹³protons/cm² to 50*10¹³ protons/cm². Heat treatment processes that areeffected at a temperature of 350 to 550° C. may be carried out betweenthe proton irradiations or after the proton irradiations.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in more detail below in exemplary embodimentwith reference to the figures, in which:

FIG. 1 shows the dopant concentration profile in the case of a diodewith a rated reverse voltage of 1200 V with a field stop zone(punch-through embodiment).

FIG. 2 shows an example of a dopant concentration profile of a fieldstop layer of a semiconductor device according to the invention.

FIGS. 3 a-3 c show the switching behavior of a semiconductor deviceaccording to the invention in comparison with a reference device usingthe example of a diode.

FIG. 4 shows a schematic diagram of the method for fabricating a diodeaccording to the invention.

FIG. 5 shows a schematic diagram of the method for fabricating an IGBTaccording to the invention.

DESCRIPTION

The exemplary application of a diode shall be discussed first.

The method according to the invention for fabricating the field stopzone in this case provides for simulating the stepped field stop zonedoping profile 1 known in principle from FIG. 1 by the doping effect ofone or more proton irradiations with at least one subsequent heattreatment step or heat treatment steps taking place between theirradiations. One advantage is that in the case of irradiation withprotons, it is possible to achieve relatively large depths with lowerimplantation energies than in the case of conventional dopants. Thedoping is effected predominantly in the so-called end-of-range region ofthe implantation, and to a lesser extent in the region radiated through.In the case of an implantation from the rear-side, it is possible, byway of example, with an acceleration voltage of 1.5 MeV, to effectimplantation to a depth of almost 30 μm in silicon. By varying theirradiation energy and dose, it is thus possible to produce virtuallyarbitrary, rising, falling, constant or else dopant concentrations whichhave one or a plurality of minima or maxima. Moreover, activation of aproton doping merely requires a heat treatment step at 350° C. . . .550° C., whereas conventional dopings have to be annealed at more than800° C.

It is particularly advantageous if the concentration in the field stopzone is chosen not to be too high (e.g. maximum factor of 10 to 30 timeshigher than the basic doping) and, up to shortly before the rear-sideemitter, the integral dopant dose comprising homogeneous basic dopingand field stop just reaches the breakdown charge of approximately1.8*10¹² dopant atoms/cm². The integral dopant dose is intended toexceed the breakdown charge only directly before and at the rear-sideemitter. By virtue of this choice of the dopant concentrations or theintegral dopant profile, the space charge zone reaches into thesemiconductor as far as possible, but in increasingly curbed fashion asthe reverse voltage rises. It is thus always necessary for floodingcharge to be depleted. As long as an increase in the reverse voltage byDELTA U is necessarily associated with the depletion of a charge packetDELTA Q of the flooding charge, that is to say the depletion is notchopped off, the reverse voltage cannot rise abruptly: the switchingprofile remains “soft”. By virtue of the doping profile chosen, thethickness of the diode is utilized as effectively as possible for thespace charge zone, that is to say that the softness of a diodedimensioned in this way is as good as that of a thicker diode without a“deeper” field stop (that is to say a field stop zone introduced farinto the interior of the semiconductor volume), while its losses areequally lower. In other words: with the deeply extending field stopdoping, it is possible to fabricate diodes with the same or improvedsoftness with a reduced thickness of the n-type base region.

FIGS. 3 a-3 c show the switching behavior of a 1200 V diode fabricatedaccording to the invention, with a rated current of 100 A, in comparisonwith a reference diode that does not have a proton field stop situateddeep in the semiconductor volume. Since the switching behavior is morecritical at a low bias current, a measurement was carried out here atonly 10% of the rated current and at the same time a relatively highintermediate circuit voltage (800 V).

It can clearly be discerned that the reverse current 4 of the referencedevice is chopped, while the reverse current of the component 5according to the invention has a return with a moderate dI/dt (change incurrent per change in time). A particularly good indicator of currentchopping is the gate voltage of the auxiliary switch, since it isdisturbed greatly by the current chopping of the diode: the gate voltageof the reference (curve 6) oscillates to a significantly greater extentthan that of the diode according to the invention (curve 7). A possibleharmful influence on the adjacent components becomes particularly clearhere because the gate voltage, as a result of the oscillations of thereference diode, momentarily even exceeds the switch-on threshold of theauxiliary switch, but the latter in this case is too sluggish to reactimmediately—and is possibly destroyed. The reference numerals 8 and 9denote the substrate voltage profiles of the diode according to theinvention and the reference diode.

The proton doses of the individual implantations that are suitable forrealizing the proposed concept typically vary in the range of 0.5 . . .50*10¹³ protons/cm², and the aggregate dose of all the implantationstypically varies in the range of 5 . . . 50*10¹³ protons/cm². The heattreatments are intended to be carried out at temperatures in the rangeof between 350° C. and 550° C. over a few tens of minutes to a fewhours, in which case a targeted widening of the donor peaks realized canbe realized as the temperature budget increases, and the maximum dopantconcentration in the end-of-range region of the implantation is reduced,moreover, as the temperature increases above approximately 400° C. Atthe same time, the carrier lifetime is also increased in the regionradiated through, as a result of intensified annealing of theimplantation defects.

The highest dose, which serves for ensuring the blocking capability, maypreferably be implanted directly before the emitter. As a result of theradiation damage of the preceding implantations with higher energy, alateral propagation of the hydrogen-induced donors is even to bereckoned with here. Consequently, even particles that have masked theshallow proton implantation can be underdiffused and, consequently,reverse currents can be decreased or the yield in a reverse current testcan be increased.

In this case, the shallowest implantation may either directly adjoin theemitter; however, it may also be spaced apart from the latter. Thus, thedepth of the implantation maximum of said shallowest implantation mayperfectly well be at a distance of up to approximately one third of thebase width of the chip from the rear-side emitter, in order, betweenthis doping peak and the rear-side emitter, to protect a reservoir withhigher charge carrier flooding against the field punch-through.

According to the invention, then, in the case of a diode, a graded fieldstop zone is produced, which enables a soft turn-off. What is essentialis that for this purpose at least two proton energies are necessary andthe integral dopant dose reaches the breakdown charge only near to thecathodal end of the field stop zone.

The exemplary application of an IGBT shall now be discussed. Firstly,the corresponding prior art will be considered.

The intention is to realize a field stop zone in IGBTs which, on the onehand, guarantees a sufficient blocking capability of the components, buton the other hand also enables satisfactory dynamic properties—such ase.g. a sufficiently soft turn-off behavior and a high short-circuitloading capacity. In particular, said field stop zone is also intendedto be realized at temperatures lying below 550° C., in order for thefield stop zone not to be produced until in the largely finishedprocessed silicon wafer. This facilitates the use of relatively thinsilicon wafers, which entails a reduction of the overall losses in thecase of IGBTs having reverse voltages <1800 V.

Nowadays field stop zones are fabricated primarily by means ofimplantation methods and subsequent diffusion steps, but the processtemperatures are relatively high. In the case of a phosphorus diffusion,temperatures >1100° C. are required in order to produce a sufficientlydeep field stop zone with an economically tenable outlay. Even in thecase of a direct high-energy implantation into the corresponding depth,temperatures of above 700° C. are still required in order to anneal theradiation damage and to activate the doping.

It has already been proposed (document U.S. Pat. No. 6,482,681 B1) tofabricate such a stop zone by means of one or more proton irradiationsteps, energies lying between 100 and 500 keV being used in theapplication of a plurality of proton irradiations. This is becauseproton irradiations have the property of producing donors particularlyin the so-called “end-of-range” region, to be precise all the moredonors the higher the irradiation dose.

Corresponding experiments have revealed that, for simultaneouslyrealizing a soft turn-off behavior and a sufficient short-circuitstrength, a doping profile that leads out deeply is necessary for thefield stop zone, in a similar manner to that as can be realized e.g.with a phosphorus diffusion at significantly higher temperatures incombination with longer diffusion times.

Therefore, when using a proton irradiation for producing this(preferably) n-doped field stop zone from the collector side, it isabsolutely necessary to use a multiple implantation in which the maximumenergy is at least 1 MeV. In this context, e.g. a triple (a) orquadruple (b) proton irradiation with the following energy graduationswould be advantageous: [0043] a) 300 keV, 500 keV, 1 MeV; [0044] b) 300keV, 500 keV, 1 MeV, 1.25 MeV.

This is because if the maximum energy of 500 keV is chosen, neither thesoftness of the turn-off capability nor the required short-circuitstrength is provided.

Typical annealing temperatures for this irradiation lie in the range ofbetween 350 and 420° C. If, by contrast, the annealing temperature ischosen in the range of between 420 and 550° C., the (preferably) n-dopedpeak caused by the proton irradiation is widened considerably, so thatthe number of irradiation steps may possibly be reduced. A desirableside effect of this procedure may consist in the raising of the carrierlifetime in the region radiated through as a result of the increasingannealing of the irradiation-induced defects in silicon, which lower thecarrier lifetime.

It is also conceivable to realize the peak lying the deepest below thecollector-side surface by means of a proton irradiation from the frontside of the IGBT, preferably before the silicon wafer is brought to itsfinal thickness by thinning by grinding. The second deepest peak maypossibly also be realized in this way. A targeted widening of the peakor peaks at temperatures lying between 400 and 550° C. is appropriatehere. Front-side processes whose permissible maximum temperature liesbelow this annealing temperature can then be carried out after theproton irradiation and this heat treatment. The irradiation energiesrequired for this are significantly higher, however, to be precise allthe more higher the thicker the silicon wafer, that is to say the higherthe required blocking capability of the components.

The irradiation doses should be chosen such that the deep-lying peaksshould be produced rather with a low dose, to be precise typically inthe range of between 1*10¹³ and 7*10¹³ protons/cm², while a high doseabove approximately 5*10¹³ protons/cm² should be used in particular forproducing the peak or the two peaks lying closely below the wafersurface (with respect to the rear-side of the device), in order toproduce a sufficient number of donors so that the breakdown charge isexceeded and the blocking capability of the components is ensured. Inthis case, it is necessary to take account of the fact that only a smallpercentage (approximately 1 to 2%) of the implanted hydrogen dose isconverted into donors.

The irradiation with a plurality of energies, primarily also higherenergies, has the advantage that, below particles which are usuallysituated on the wafer surface during the proton irradiation, in anyevent enough defects (induced by the irradiation) are also presentwhich, in combination with a lateral diffusion of the implanted hydrogenatoms also in the region shaded by the undesirable particles, makeavailable enough donors for ensuring the blocking capability of theIGBT. This is because both the irradiation-generated defects (inparticular vacancies) and the implanted hydrogen atoms are required forforming said donors. In order to further safeguard the blockingcapability, it is also possible to effect an additional implantation ofn-doping elements, such as e.g. phosphorus, sulfur or selenium atoms,whose—albeit slight at the temperatures used—lateral diffusion reliablyprecludes the negative consequences of the shading effects describedabove.

According to the invention, therefore, a multiple implantation withprotons is carried out in the case of IGBTs, the irradiation energiesbeing chosen so as to produce a relatively deep doping profile (a dopingprofile extending deep into the semiconductor profile) of the field stopzone thus formed, which in turn leads to very good electrical propertiesof the irradiated IGBTs. The highest implantation energy used should inthis case be at least 1 MeV, and the lowest should be a maximum of 500keV.

FIG. 2 shows an example of a dopant concentration profile 3 of a fieldstop layer of a semiconductor device according to the invention, whichcan equally be used for a diode or an IGBT. A plurality of maxima/minimacan be seen, the height of the maxima increasing in the direction towardthe second connection region.

FIG. 4 shows a schematic diagram of the method for fabricating a diodeaccording to the invention. A diode 10 has a first connection region 11(preferably metal) and a second connection region 12 (preferably metal).A semiconductor volume 13 is arranged between the first connectionregion 11 and a second connection region 12. The first connection region11 is adjoined by an anode region 15 (semiconductor region) and thesecond connection region 12 is adjoined by a cathode region 16(semiconductor region).

Preferably, the thickness D1 of the field stop zone 14 is a maximum ofone third of the base width B1 of the semiconductor volume, the basewidth being defined as the distance between the last pn junction 17,before the field stop zone 14 (relative to a direction pointing from thefirst connection region 11 to the second connection region 12) and theinterface 18 of the field stop zone 14 which faces the second connectionregion 12. In order to produce a field stop zone 14 having the thicknessD1 within the semiconductor volume 13 having the thickness D2, protonsare radiated through the rear side of the diode 10, that is to say thesecond connection region 12, using a plurality of implantation energies,in which case, in principle, the first connection region 11 could alsobe radiated through. As a result, the integral of the ionized dopantcharge over the semiconductor volume 13, proceeding from an interface 17(pn junction) of the anode region 15 that faces the second connectionregion 12, in the direction of the second connection region 12, producesa quantity of charge corresponding to the breakdown charge of thesemiconductor device 10 only near the interface 18 of the field stopzone 14 which faces the second connection region 12.

FIG. 5 shows a schematic diagram of the method for fabricating an IGBTaccording to the invention. An IGBT 20 has a first connection region 11(preferably metal) and a second connection region 12 (preferably metal).A semiconductor volume 13 is arranged between the first connectionregion 11 and a second connection region 12. The first connection region11 is adjoined by a cell region 21 (semiconductor region), and thesecond connection region 12 is adjoined by a rear-side emitter region 22(semiconductor region). The cell region 21 has, in a known manner sourceregions 23, body regions 24, a gate 25 and an insulation layer 26.

In order to produce a field stop zone 14 having the thickness D1 withinthe semiconductor volume 13 having the thickness D2, protons areradiated through the rear side of the IGBT 20, that is to say the secondconnection region 12, using a plurality of implantation energies, inwhich case, in principle, the first connection region 11 could also beradiated through. As a result, the integral of the ionized dopant chargeover the semiconductor volume 13, proceeding from an interface 27 (pnjunction) of the cell region 21 (to put it more precisely the bodyregions 24) that faces the second connection region, in the direction ofthe second connection region 12, produces a quantity of chargecorresponding to the breakdown charge of the semiconductor device 20only near the interface 28 of the field stop zone 14 which faces thesecond connection region 12.

The penetration depths of the protons that are reached during protonirradiation are related to one another such that the second deepestpenetration depth, compared with the deepest penetration depth, has adistance of 30% to 60% of the value of the maximum penetration depth. Itis thus possible to obtain a particularly good softness during theswitching of the semiconductor device.

1. A method for fabricating a field stop zone within a semiconductordevice, the method comprising: providing a semiconductor devicecomprising a first and second connection region, and a semiconductorvolume arranged between the first and second connection regions;performing a plurality of proton irradiations on the semiconductorvolume, each of the plurality of proton irradiations comprising animplantation energy and a proton dose and at least one protonirradiation comprising an implantation energy of at least 500 keV;performing at least one heat treatment on the semiconductor volume, theat least one heat treatment comprising a temperature; and selecting theimplantation energy and the proton dose of each proton irradiation ofthe plurality of proton irradiations and the temperature of the at leastone heat treatment step so as to produce a dopant concentration profilesuch that an integral of an ionized dopant charge over the semiconductorvolume, proceeding from a pn junction provided between the firstconnection region and a field stop zone, in the direction of the secondconnection region, substantially reaches a quantity of chargecorresponding to a breakdown charge of the semiconductor device onlynear an interface of the field stop zone that is closest to the secondconnection region.
 2. The method of claim 1, wherein the semiconductordevice is an IGBT device; and wherein a highest implantation energy usedis approximately at least 1 MeV, and a lowest implantation energy usedis approximately at most 500 keV.
 3. The method of claim 1, wherein theperforming a plurality of proton irradiations step further comprises:performing three proton irradiations on the semiconductor volume atapproximately the following implantation energies: 300 keV, 500 keV, and1 MeV.
 4. The method of claim 1, wherein the performing a plurality ofproton irradiations step further comprises: performing four protonirradiations on the semiconductor volume at approximately the followingimplantation energies: 300 keV, 500 keV, 1 MeV and 1.25 MeV.
 5. Themethod of claim 1, wherein a lowest implantation energy used isapproximately at least 500 keV.
 6. The method of claim 1, wherein theperforming a plurality of proton irradiations step further comprises:performing three proton irradiations on the semiconductor volume in thefollowing ranges for the implantation energies respectively: between 500keV and 700 keV, between 1300 keV and 1700 keV, and between 1800 keV and2400 keV.
 7. The method of claim 1, wherein the performing a pluralityof proton irradiations step further comprises: performing four protonirradiations on the semiconductor volume in the following ranges for theimplantation energies respectively: between 300 keV and 500 keV, between500 keV and 900 keV, between 900 keV and 1300 keV, and between 1200 keVand 1700 keV.
 8. The method of claim 1, wherein the implantation energyof at least one proton irradiation is above 2 MeV and the temperature ofat least one heat treatment step is equal or above 400° C.
 9. The methodof claim 1, wherein the performing at least one heat treatment stepfurther comprises: performing the at least one heat treatment at atemperature of approximately 350 to 550° C., the at least one heattreatment being carried out between proton irradiations or after theproton irradiations.
 10. The method of claim 1, wherein the performing aplurality of proton irradiations on the semiconductor volume step,further comprises: performing at least one proton irradiation at anirradiation dose of approximately 1*10¹³ protons/cm² to produce dopingregions situated deeper in the semiconductor volume; and performing atleast one proton irradiation at an irradiation dose of approximately7*10¹³ protons/cm² to produce doping regions situated nearer to asurface of the semiconductor volume.
 11. The method of claim 1, whereinthe semiconductor device comprises a diode, and wherein the irradiationdoses of the plurality of proton irradiations are between approximately0.5*10¹³ to 20*10¹³ protons/cm².
 12. The method of claim 1, wherein thesemiconductor device comprises a diode, and further wherein a sum of theirradiation doses of the plurality of proton irradiations is betweenapproximately 2*10¹³ protons/cm² to 50*10¹³ protons/cm2.
 13. The methodof claim 1, wherein the plurality of proton irradiations furthercomprising a deepest penetration depth and a second deepest penetrationdepth, the second deepest penetration depth being approximately 30% to60% of the value of the deepest penetration depth.
 14. The method ofclaim 1, further comprising: selecting the implantation energy and theproton dose of each proton irradiation of the plurality of protonirradiations and the temperature of the at least one heat treatment stepso as to produce a dopant concentration profile such that the dopantconcentration profile includes one maxima within the field stop zone.15. The method of claim 1, wherein a sum of the electrically activedopant dose created by the plurality of proton irradiations is betweenapproximately 3*10¹¹ donors/cm² to 1*10¹² donors/cm².
 16. The method ofclaim 1, wherein the plurality of proton irradiations further comprise adeepest penetration depth of at least 6 μm.
 17. The method of claim 1,further comprising: selecting the implantation energy and the protondose of each proton irradiation of the plurality of proton irradiationsand the temperature of the at least one heat treatment step so as toproduce a dopant concentration profile such that in a reversed biasedmode of the semiconductor device the gradient of the electric fieldwithin the field stop zone is larger than the gradient of the electricfield within the drift zone.
 18. The method of claim 1, wherein theproton dose of a proton irradiation is lower for a higher implantationenergy.
 19. The method of claim 1, wherein at least one heat treatmentis performed by laser annealing.
 20. The method of claim 1, furthercomprising forming a metal layer on a surface of the semiconductordevice, wherein at least one heat treatment is performed before theforming of the metal layer and after at least one proton irradiation.21. The method of claim 1, wherein the thickness of the field stop zoneis at least 10% of the thickness of the semiconductor volume arrangedbetween the first and second connection regions.
 22. The method of claim1, wherein the distance of two adjacent penetration depths of two protonirradiations is at least 5 μm.